Molex to PWM

[Atomicdonut17]

Welp, I have a case that comes with x2 120mm Blue LED case fans, which are both powered by a 4-pin MOLEX. While that would normally not be a problem, and it's frankly only hypothetical, I want as little cable mess as possible. So, I figure if I purchase some sort of MOLEX-to-PWM, it would plug into one mobo header, and be able to be controlled through the mobo.

Is that how it would work? Thanks.

 

[gasaraki]

theoretically that should work if the motherboard knows how to control fans only via voltage regulation. (so 3 pin method)

 

[Paperdoc]

gasaraki is right. But to add / clarify, you do NOT need a way to "convert" your fans to PWM type. In fact, you cannot do exactly that. A PWM fan has a different find of motor than the ones your case came with, and that is why it can use a PWM signal. Your fans are most like the older style 3-pin fans that are controlled by the Voltage supplied to it from a mobo header. So, any adapter that can "convert" your fans' Molex male connector into a standard female 3-pin fan female connector can do some of what you want. Unfortunately, getting such an adapter may be very difficult. The common adapters on the market do the opposite - they convert a fan's female 3-pin connector into a Molex male 4-pin connector so that you can plug a common fan into a PSU Molex output. You might have to buy a couple of adapter cables and cut and splice things to make you own. If you need advice on what to connect in such D-I-Y adapter construction, ask here.

BEFORE doing that, you also need to verify something else you would need to make this work. A 3-pin fan can have its speed controlled by a mobo header ONLY if that header uses Voltage Control Mode.. These days most mobo fan headers have 4 pins, BUT that does not guarantee they use PWM Mode. Many, in fact, do NOT use the 4-pin PWM Mode for control and act like true 3-pin headers. The only way to tell how YOUR mobo does this is by reading for details in its manual (and sometimes even then the manual is not clear). So post back here exactly what make and model of mobo you have so we can help determine whether your mobo's SYS_FAN header(s) can provide the Voltage Control Mode you will need.

Then there's s third consideration. Standard fans (either 3-pin or 4-pin) send out a speed signal on their Pin #3 going to the mobo for measurement of fan speed. This is used, among other things, for failure checking - if the fan does not send its speed signal to the mobo header, the mobo may alarm you that the fan has failed. But the fans that came with your case (and with 4-pin Molex connectors on them) do NOT have any speed signal output line, so even using some sort of adapter they cannot send that signal to your mobo. Hence, if you get this to work, your mobo may still tell you the fan has failed. In most mobos there us a way to tell it to Ignore the fan's speed signal so it does not send you such useless warnings. We'll look for that, too, in your mobo manual.

 

[the nerd 389]

As mentioned above, you want the 3-pin connector. 4-pin PWM requires totally different circuitry in the fan.

If you're comfortable with wire strippers and a crimper:
https://www.moddiy.com/products/modDIY-Female-3%252dPin-Fan-Connector-%28Molex-%232510%29-with-Pins.html

If you don't have the crimper for those pins, it's here:
https://www.moddiy.com/products/Professional-Molex-Crimping-Tool.html

The crimpers are not very cheap, but for clean cable routing, it is really handy. With it, some connectors, and some wire strippers, you can cut your cables to the exact length you need for that build.